Protein concentrates from plain, aromatic and pigmented rice cultivars: Functional, thermal and morphological characterization

Abstract

Protein is a vital nutrient required for growth and development of human population. It is well recognised that a significant cause of malnutrition is a lack of protein in human diet. Plant based proteins are becoming an excellent substitute for meat proteins in the development of functional foods at a fair price. When it comes to plant-based sources of high-quality protein, rice is regarded as a useful option because of its hypoallergenic properties, adequate amino acid balance, and high protein content. Therefore, protein concentrates were obtained from plain (SR-4, K-39), aromatic (Mushq Budij) and pigmented (Zhag) rice cultivars of Kashmir. Significant (p<0.05) difference was observed in protein (70.40–74.23 g/100 g) and ash (2.90–3.50 g/100 g) contents of protein concentrates isolated from different rice cultivars. Zhag protein had the lowest ‘L’ value (40.20). However, it had the highest emulsifying activity (47.29 m2/g) and emulsion stability index (13.38 min) at neutral pH. Moreover, water absorption capacity was highest for K-39 protein (1.90 g/g). Zhag protein had the highest protein solubility and foaming stability under acidic pH conditions. Zhag protein had the highest denaturation temperature (81.70 °C) and denaturation enthalpy (9.55 Jg−1). No sharp peaks were observed in the X-ray diffractogram (XRD), indicating amorphous behaviour of protein powder. Pearson's correlation revealed positive correlation between emulsifying activity indices (EAI) at pH 7 and protein solubility at pH 8 (r = 0.955, p<0.05). Surface hydrophobicity (SH) of RPCs was found to be positively correlated with EAI at pH 3 (r = 0.991, p<0.01) and foaming capacity (FC) at pH 8 (r = 0.994, p<0.01), respectively. It can be concluded from the present study that protein concentrate from pigmented rice cultivar was superior to other samples in terms of functionality and thermal attributes.